16.7.3 Interface To fork(), wait() and waitpid()

The fork extension adds three functions, as follows.

@load "fork"

This is how you load the extension.

pid = fork()

This function creates a new process. The return value is zero in the
child and the process-ID number of the child in the parent, or -1
upon error. In the latter case, ERRNO indicates the problem.
In the child, PROCINFO["pid"] and PROCINFO["ppid"] are
updated to reflect the correct values.

ret = waitpid(pid)

This function takes a numeric argument, which is the process-ID to
wait for. The return value is that of the
waitpid() system call.

ret = wait()

This function waits for the first child to die.
The return value is that of the
wait() system call.